Microbiology Flashcards
What colour to Gram Positive organisms stain on a Gram Stain and why?
PURPLE. They stain well due to thick peptidoglycan layer.
Do gram positive organisms produce endotoxin or exotoxin?
Exotoxin which is exported from the cell
What are streptococci? How are they arranged?
Gram postitive aerobic cocci in strips
What is alpha-haemolysis and which organisms cause it?
Partial haemolysis. Caused by Strep. Pneumoniae and Strep Viridans.
What is beta-haemolysis and which organisms cause it?
Complete haemolysis. Caused by group A and group B strep
What is gamma-haemolysis and which organisms cause it?
No haemolysis. Caused by enterococcus
What are staphylococci? How are they arranged?
Gram positive aerobic cocci in clusters
What organisms are coagulase positive?
Staph.Aureus (wound + skin infections)
What organisms are coagulase negative?
All other staph, e.g. skin commensals
Name an aerobic gram positive bacilli
Bacillus cereus (food poisoning from rice)
Name an anaerobi bacilli
Clostridium Difficile (Antibiotic associated colitis)
What colour do gram negative organisms stain a gram stain and why?
PINK. Stain less well as thinner peptidoglycan layer doesn’t retain stain well
Do gram negative organisms produce endotoxin or exotoxin?
Endotoxin. It is part of the cell wall.
Which gram negative organisms are strict aerobes?
Legionella
Pseudomonas
Name 2 gram negative diplococci
Neisseria gonorrhoea
Neisseria meningitides
What are the gram negative gut commensals?
E.Coli
Klebsiella
Proteus
What are the gram negative gut pathogens?
E.Coli 0157
Salmonella
Shigella
What toxin does E.Coli 0157 produce and what can it cause?
VEROTOXIN. Causes haemolytic uraemic syndrome. Commonest cause of renal failure in kids under 5
Name a strict anaerobic gram negative Bacilli
Bacteroids
What gram negative organism causes whooping cough?
Bordetella Pertussis
What gram negative organism causes COPD exacerbations?
Haemophilus Influenza
What does bacteriostatic mean?
An antibiotic which inhibits cell growth
What does bactericidal mean?
An antibiotic which kills bacteria directly
Which classes of antibiotic work on the cell wall?
Penicillins
Cephalosporins
Glycopeptides
Which classes of antibiotic work on bacterial DNA?
Metronidazole
Trimethoprim
Fluoroquinolone’s
Which classes of antibiotic inhibit protein synthesis?
Macrolides
Aminoglycosides
Tetracyclines
Describe 3 features of Penicillins
Bactericidal
Safe in pregnancy
Excreted via kidneys
What does flucloxacillin treat?
Staph + strep only
What does Temocillin treat?
Gram negative organisms ONLY. Active against ESBL producing organisms
What does amoxicillin treat?
Treats both gram negative and gram positive organisms. Broad spectrum but destroyed by beta lactamase
Describe 3 features of cephalosporins?
Bactericidal
safe in pregnancy
excreted via kidneys
Describe 3 features of glycopeptides, e.g. vancomycin
Bactericidal
safe in pregnancy
excreted via kidneys
only active against gram POSITIVE organisms
Name some macrolides
Erythromycin
Clarithromycin
Azithromycin
Which macrolide is safe in pregnancy?
Erythromycin
Are macrolides bactericidal/bacteriostatic and how are they excreted?
Bacteriostatic
Excreted via liver
Name 4 features of aminoglycosides, e.g. gentamicin
Must be given IV or IM
Bactericidal
NOT safe in pregnancy
Excreted via kidneys
What are the side effects of gentamicin?
Damage to 8th cranial nerve + damage to kidneys
Which antibiotics can cause C.Diff infection?
Cephalosporins
Clindamycin
Co-amoxiclav
Ciprofloxacin
